INVESTMENTS (Gross Unrealized Losses and Related Fair Values for Debt and Equity Securities, Grouped by Duration of Time in Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair value [Abstract]
Less than 12 months	$ 126,775	$ 219,575
12 months or longer	1,724	3,984
Total fair value	128,499	223,559
Gross unrealized losses [Abstract]
Less than 12 months	1,668	4,152
12 months or longer	105	70
Total gross unrealized losses	1,773	4,222
Debt Securities [Member]
Fair value [Abstract]
Less than 12 months	117,765	214,874
12 months or longer	1,028	3,550
Total fair value	118,793	218,424
Gross unrealized losses [Abstract]
Less than 12 months	1,037	3,899
12 months or longer	13	35
Total gross unrealized losses	1,050	3,934
United States Government Obligations and Authorities [Member]
Fair value [Abstract]
Less than 12 months	48,333	45,255
12 months or longer	98	111
Total fair value	48,431	45,366
Gross unrealized losses [Abstract]
Less than 12 months	479	850
12 months or longer	5	3
Total gross unrealized losses	484	853
Obligations of States and Political Subdivisions [Member]
Fair value [Abstract]
Less than 12 months	24,012	103,724
12 months or longer		1,007
Total fair value	24,012	104,731
Gross unrealized losses [Abstract]
Less than 12 months	228	2,066
12 months or longer		1
Total gross unrealized losses	228	2,067
Corporate [Member]
Fair value [Abstract]
Less than 12 months	43,646	59,970
12 months or longer	930	2,427
Total fair value	44,576	62,397
Gross unrealized losses [Abstract]
Less than 12 months	320	864
12 months or longer	8	31
Total gross unrealized losses	328	895
International [Member]
Fair value [Abstract]
Less than 12 months	1,774	5,925
12 months or longer		5
Total fair value	1,774	5,930
Gross unrealized losses [Abstract]
Less than 12 months	10	119
Total gross unrealized losses	10	119
Equity Securities [Member]
Fair value [Abstract]
Less than 12 months	9,010	4,701
12 months or longer	696	434
Total fair value	9,706	5,135
Gross unrealized losses [Abstract]
Less than 12 months	631	253
12 months or longer	92	35
Total gross unrealized losses	$ 723	$ 288